This invention relates in general to waveguides, and in particular to novel methods for fabricating optical waveguides.
Waveguides constrain or guide the propagation of electromagnetic waves along a path defined by the physical construction of the waveguide. The use of optical channel waveguides is widespread in integrated optical circuits. In particular, an optical channel waveguide provides both vertical and lateral confinement of an optical wave while allowing low-loss signal propagation.
An optical channel waveguide having small cross-sectional dimensions allows high optical power densities to be established for moderate optical input powers while the waveguiding nature provides potentially long interaction lengths. This combination of effects is extremely attractive for a variety of optical functions such as second harmonic generation, optical amplification, wavelength conversion, and phase modulation (when an appropriate electrode geometry is incorporated).
In general, a goal of waveguide fabrication is to produce waveguides which support a single guided mode of propagation of the electromagnetic waves. A number of techniques have been used with considerable success to fabricate optical channel waveguides. These include ion-exchange in glass substrates, ion indiffusion or proton exchange in LiNbO3 substrates, pattern definition by laser ablation, photolithography of spun polymer films, and epitaxial growth and selective etching of compound semiconductor films.
A drawback of these techniques is that they cannot be used with a significant number of useful optical materials, e.g., many laser crystals. Another drawback of these prior art techniques is that the equipment required to fabricate the optical waveguide is expensive.
Therefore, there is a need for methods for forming optical waveguides from separate preformed optical materials in which the methods comprise a plurality of mechanical processing steps, e.g., lapping, polishing, and/or dicing, and bonding steps, e.g., attaching with adhesives. Such methods are adaptable to fabrication of optical waveguides from any, if not all, optical materials. Furthermore, such methods are suitably performed using readily available and inexpensive equipment.
Pursuant to the present invention, the shortcomings of the prior art are overcome and additional advantages provided through the provision of a method for forming an optical waveguide from separate preformed materials. For example, one embodiment of the method for forming an optical waveguide comprises the steps of providing an assembly comprising an optical material between a first support substrate and a second support substrate, providing a third support substrate and a fourth support substrate, and attaching to opposite surfaces of the assembly, a third support substrate and a fourth support substrate, wherein the opposite surfaces each comprise the first support substrate, the optical material, and the second support substrate.
In one expect of the invention, the step of providing the assembly comprises providing the optical material comprising a polished surface, attaching the polished surface to the first substrate, thinning and polishing a second surface of the optical material, and attaching a second support substrate to the second polished surface.
In another aspect of the invention, the step of attaching opposite surfaces of the assembly between a third support substrate and a fourth support substrate comprises the steps of polishing a surface of the assembly, wherein the surface comprises the first support substrate, the optical material, and the second support substrate, attaching the polished surface of the assembly to the third support substrate, thinning and polishing an opposite surface of the assembly, wherein the opposite surface comprises the first support substrate, the optical material, and the second support substrate, and attaching the opposite polished surface to the fourth support substrate.
In another aspect of the present invention, the method further comprising the step of dicing the first assembly to form a plurality of assemblies, wherein each of the plurality of assemblies is attachable to separate support structures for forming separate optical waveguides.
In another embodiment of the present invention for forming a waveguide, the method comprising the steps of providing an optical material, thinning and polishing the optical material to form a core comprising a plurality of longitudinally extending surfaces, providing a plurality of support substrates, and adhesively attaching the plurality of support substrates to the longitudinally extending surfaces of the core. Desirably, the plurality of support substrates are attached to the plurality of longitudinally extending surfaces of the optical material with an adhesive. The optical material may comprise a high refractive index, and the plurality of support substrates and/or the adhesive may comprise a low refractive index.
The optical waveguides fabricated according to the present invention, when the core comprises an optical gain material, are particularly suitable for lasers and amplified spontaneous emission (ASE) sources for imaging and spectroscopy applications where multi-mode fibers are used to handle high power, as well as test instrumentation for the telecommunications and cable television industries where single mode delivery is required. Additional and detailed uses of the optical waveguides of the present invention are described in the above-incorporated application.